Due to the rapid development of data storage devices such as conventional hard disks and optical disks, information storage devices having recording densities of 1 Gbit/inch2 or greater have been developed. Accordingly, higher capacity information storage devices are required. However, conventional information storage devices may have limited recording density due to super-paramagnetic limits and/or laser diffraction limits of optical disks. Recently, research has been conducted to develop an information storage device having a recording density of 100 Gbit/inch2 or greater in an effort to overcome the diffraction limit of light using near-field optics technology.
Higher capacity information storage devices using tip-shaped probes that can be observed by atomic force microscopy (AFM) are also being researched. The tip-shaped probes of such devices may be reduced to several nanometers in size, and may be used to observe surface minute structures on an atomic level. Theoretically, terabyte information storage devices may be manufactured using such tip shaped probes. One important factor in an information storage device using tip-shaped probes may be the type of recording medium and the recording method. An example of a recording medium may be a ferroelectric recording medium.
FIG. 1 is a cross-sectional view of a conventional ferroelectric recording medium. Referring to FIG. 1, a conventional ferroelectric recording medium may include a bottom electrode 4 and a recording medium layer 8 sequentially stacked on a substrate 2. The recording medium layer 8 may be a ferroelectric thin layer formed of PbTiO3, PbZrxTi(1-x)O3 (PZT), or SrBi2Ta2O9(SBT). When a voltage pulse is applied between the bottom electrode 4 and an AFM tip 9 is disposed above the recording medium layer 8, the polarization of the recording medium layer 8 may be locally changed. Depending on the polarity of the voltage, data corresponding to upward or downward polarization may be recorded, and the polarization may be detected using resistive probes, for example.
When a ferroelectric thin layer is used as a recording medium, the recording speed of data may be higher, the power consumption may be very low, and repeated recording may be possible. However, a ferroelectric recording medium may have poor data maintenance characteristics and/or poor surface roughness characteristics. For example, when the surface roughness characteristics are poor, more time is needed to control the distance between the AFM tip and the recording medium, thereby slowing the reading/recording speed and/or possibly tearing the tip.
Due to one or more of the above problems, a ferroelectric thin layer having good crystalline characteristics, good surface roughness characteristics and higher recording density data storage capacity, as well as a method of manufacturing the ferroelectric thin layer are needed. Due to the properties of ferroelectric materials and the limitations of known manufacturing processes of ferroelectric materials, conventional methods of manufacturing ferroelectric thin layers do not overcome these problems.
Recently, in an effort to realize new higher capacity storage or recording media, various methods have been studied, such as depositing a ferromagnetic material in a predetermined region and probing it, or reading data thermomechanically using melting of polymers. However, in the case of ferromagnetic storage or recording media, when the storage space is reduced, the ferromagnetic material may be converted to a paramagnetic material, and thus there are limitations in the storage capacity. Also, when reading data thermomechanically using the melting of polymers, there are also limitations in the storage capacity when heat is transferred to the polymers not only in a vertical direction but also in a horizontal direction.